240 THE FARMER OF TO-MORROW 



"The soil, speaking in the widest sense, is 

 then not only the ultimate exhaustless source 

 of mineral (fixed) food of vegetation, but is 

 the storehouse and conservatory of this food, 

 protecting its resources from waste and too 

 rapid use." 



In 1879 the same author (How Crops 

 Feed) said: 



"Those bodies which are most rare and pre- 

 cious to the growing plant are by the soil con- 

 verted into and retained in a condition not of 

 absolute, but of relative solubility, and are 

 kept available to the plants by the continued 

 circulation in the soil of the more abundant 

 saline matters." 



If red ink is passed through soil it is no 

 longer red ink. It is clear water, so avid are 

 the soil grains for certain elements. If nitrate 

 of silver is passed through finely divided char- 

 coal the solution that leaches out consists of 

 nitric acid, and with a glass one can discover 

 fine spangles of silver in the charcoal. The 

 absorptive power of sand was used in Bacon's 

 day as a means of extracting salt from sea 

 water. The commercial use of this property 

 is common in our everyday life. We refer 



